Thinned semiconductor package and related methods

ABSTRACT

Implementations of semiconductor packages may include a die having a first side and a second side opposite the first side, a first metal layer coupled to the first side of the die, a tin layer coupled to the first metal layer, the first metal layer between the die and the tin layer, a backside metal layer coupled to the second side of the die, and a mold compound coupled to the die. The mold compound may cover a plurality of sidewalls of the first metal layer and a plurality of sidewalls of the tin layer and a surface of the mold compound is coplanar with a surface of the tin layer.

BACKGROUND 1. Technical Field

Aspects of this document relate generally to semiconductor packages.More specific implementations involve thinned power semiconductorpackages with a dual side metallization structure and methods of makingsuch thinned power semiconductor packages.

2. Background

Semiconductor package fabrication processes may involve many steps. Insome processes a wafer receives one or more layers, such as electricallyconductive layers. Electrically conductive layers may be used to provideelectrical contact areas of individual semiconductor devices singulatedfrom the wafer. Electrically conductive layers may be formed usingsputtering, evaporation, or electroplating operations. Further, in someprocesses the overall size of the semiconductor package may designed tobe minimized which may result in economic benefits as well astechnological benefits.

SUMMARY

Implementations of semiconductor packages may include a die having afirst side and a second side opposite the first side, a first metallayer coupled to the first side of the die, a tin layer coupled to thefirst metal layer, the first metal layer between the die and the tinlayer, a backside metal layer coupled to the second side of the die, anda mold compound coupled to the die. The mold compound may cover aplurality of sidewalls of the first metal layer and a plurality ofsidewalls of the tin layer and a surface of the mold compound iscoplanar with a surface of the tin layer.

Implementations of semiconductor packages may include one, all, or anyof the following:

A second metal layer may be coupled between the die and the first metallayer.

A plurality of bumps may be included in the first metal layer and thetin layer.

The mold compound may cover a first and a second side of each bump ofthe plurality of bumps.

A third side, a fourth side, a fifth side, and a sixth side of the diemay be covered by the mold compound.

The backside metal layer may include copper.

The backside metal layer may include a metal alloy comprising titanium,nickel, silver, vanadium, copper, and any combination thereof.

Implementations of a method of forming a semiconductor package mayinclude forming a plurality of bumps on a first side of a wafer, forminga plurality of recesses into the first side of the wafer to a desireddepth into the wafer, and applying a mold compound to the first side ofthe wafer. The mold compound may encapsulate the plurality of bumps andfill the plurality of recesses. The method may also include thinning asecond side of the wafer to the desired depth of the plurality ofrecesses, coupling a backside metal layer to the second side of thewafer, exposing the plurality of bumps through the mold compound bygrinding the mold compound; and singulating the mold compound throughthe plurality of recesses into a plurality of semiconductor packages.

Implementations of a method for forming a semiconductor package mayinclude one, all, or any of the following:

Each bump of the plurality of bumps may include a first metal layer anda second metal layer. The first metal layer may be between the secondmetal layer and the wafer.

The method may include forming a plurality of openings in the backsidemetal layer.

The backside metal layer may include copper.

The second metal layer may include tin.

The method may include planarizing the outer surface of the plurality ofbumps with the outer surface of the mold compound.

Each bump of the plurality of bumps may also include a third metallayer, wherein the first metal layer includes copper, the second metallayer includes tin, and the third metal layer includes aluminum.

Implementations of a method of forming a semiconductor package mayinclude forming a plurality of bumps on a first side of a wafer, forminga plurality of recesses into the first side of the wafer, and applying amold compound to the first side of the wafer. The mold compound mayencapsulate the plurality of bumps and fill the plurality of recesses.The method for forming a semiconductor package may also includebackgrinding a second side of the wafer to reach the plurality ofrecesses and singulate a plurality of die from the wafer, coupling abackside metal layer to a second side of the plurality of die, exposingthe plurality of bumps through the mold compound by grinding the moldcompound, and singulating the mold compound at the plurality of recessesto form a plurality of semiconductor packages

Each bump of the plurality of bumps may include a first metal layer anda second metal layer. The first metal layer may be between the secondmetal layer and the wafer.

Each bump of the plurality of bumps may include a third metal layer.

The backside metal layer may include a metal including one of titanium,nickel, silver, vanadium, copper, and any combination thereof.

The second metal layer may include tin.

The method may include planarizing the outer surface of the plurality ofbumps with the outer surface of the mold compound.

The foregoing and other aspects, features, and advantages will beapparent to those artisans of ordinary skill in the art from theDESCRIPTION and DRAWINGS, and from the CLAIMS.

BRIEF DESCRIPTION OF THE DRAWINGS

Implementations will hereinafter be described in conjunction with theappended drawings, where like designations denote like elements, and:

FIG. 1 is a cross-section side view of a first implementation of asemiconductor package;

FIG. 2 is a cross-section side view of a second implementation of asemiconductor package;

FIGS. 3A-3G are cross-section side views illustrating a semiconductordevice following various steps of a method for forming the semiconductorpackage of FIG. 1; and

FIGS. 4A-4C are cross-section side views of a semiconductor devicefollowing various steps of a method for forming the semiconductorpackage of FIG. 2.

DESCRIPTION

This disclosure, its aspects and implementations, are not limited to thespecific components, assembly procedures or method elements disclosedherein. Many additional components, assembly procedures and/or methodelements known in the art consistent with the intended semiconductorpackages will become apparent for use with particular implementationsfrom this disclosure. Accordingly, for example, although particularimplementations are disclosed, such implementations and implementingcomponents may comprise any shape, size, style, type, model, version,measurement, concentration, material, quantity, method element, step,and/or the like as is known in the art for such semiconductor packages,and implementing components and methods, consistent with the intendedoperation and methods.

Referring to FIG. 1, a cross-section side view of a first implementationof a semiconductor package is illustrated. In various implementations,the semiconductor packages disclosed herein may include powersemiconductor devices, however, in other implementations othersemiconductor device types (transistors, microprocessors, passivecomponents, etc.) may be included in the semiconductor packages. Invarious implementations, the semiconductor package 2 includes a die 4.The die 4 may be a silicon die, and in such implementations, the silicondie could be any type of silicon die including, by non-limiting example,an epitaxial silicon die, silicon-on-insulator, polysilicon, anycombination thereof, or any other silicon-containing die material.Further, it is also understood that in various implementations a dieother than a silicon-containing die may be used, such as, bynon-limiting example, gallium arsenide, silicon carbide, galliumarsenide, or a metal-containing die. The die 4 has a first side 6 and asecond side 8 opposite the first side. In various implementations, thethickness of the die 4 is less than 50 micrometers (um), however, inother implementations the thickness of the die may be 50 um or more than50 um.

In various implementations, the semiconductor package 2 may include afirst metal layer 10 coupled to the first side 6 of the die 4. In suchimplementations, the first metal layer 10 may be, by non-limitingexample, copper, aluminum, tin, silver, gold, titanium, nickel, or anyother metal or metal alloy. In various implementations, the first metallayer 10 may be directly coupled to the first side 6 of the die 4, whilein other implementations, as is illustrated by FIG. 1, the first metallayer may be indirectly coupled to the die 4. In variousimplementations, the semiconductor package 2 may include a tin layer 12coupled to the first metal layer 10. While this disclosure primarilyrefers to a tin layer coupled over the first metal layer, it isunderstood that any other electrically and/or thermally conductivematerial, including any metal or metal alloy disclosed herein, may beused in place of the tin. Also, the tin used in the tin layer may be tinor a tin alloy, such as, by non-limiting example, tin/silver,tin/silver/copper, tin/antimony, and tin/lead. In variousimplementations, and as illustrated by FIG. 1, the tin layer 12 may bedirectly coupled to the first metal layer 10 with the first metal layer10 between the tin layer and the die 4. In other implementations the tinlayer 12 may be indirectly coupled to the first metal layer 10.

In various implementations, the semiconductor package 2 may include asecond metal layer 14 coupled between the die 4 and the first metallayer 10. In such implementations, the semiconductor package 2 includesat least three metal layers over the die 4. The second metal layer 14may be any type of metal or metal alloy disclosed herein. In particularimplementations, the second metal layer may include tin or a tin alloy,such as, by non-limiting example, tin/silver, tin/silver/copper,tin/antimony, and tin/lead. In other particular implementations, thesecond metal layer 14 may include aluminum, the first metal layer 10 mayinclude copper, and the tin layer 12 may be over and coupled to thecopper layer.

In various implementations, the tin layer 12 and the first metal layer10 may be formed into and include a plurality of bumps/studs 16. Inimplementations including a second metal layer 14 between the firstmetal layer 10 and the die 4, the second metal layer 14 may also bepatterned to form a portion of the plurality of bumps 16. In particularimplementations, not all three metal layers are patterned to form aplurality of bumps, but only the two outermost metal layers (inimplementations having three or more metal layers over the die 4)include the plurality of bumps. In still other implementations, only thetin layer 12 may be patterned to form or include the plurality of bumps.In various implementations, and as illustrated by FIG. 1, the pluralityof bumps 16 may include two bumps, however, in other implementations theplurality of bumps may include more than two bumps.

In various implementations, rather than having a plurality of metallayers forming the bumps as illustrated by FIG. 1, a single metal ormetal alloy layer, including, by non-limiting example, copper, aluminum,tin, a solder, or any combination thereof, may form the plurality ofbumps and may be directly coupled to the die 4. In otherimplementations, and as illustrated by FIG. 1, each bump of theplurality of bumps 16 may include multiple layers with a tin layer 12coupled over the copper layer. In such implementations, thesemiconductor package 2 may have the benefit of being able to bond toexternal connections through the tin layer 12 while also maintaining thebenefit of having a copper bump or stud. In various implementations, thetin layer 12 may be much thinner than the first metal layer 10, while inother implementations, the tin layer 12 may be as thick as or thickerthan the first metal layer 10. In implementations with a second metallayer 14 coupled between the first metal layer 10 and the die 4, thesecond metal layer may be less thick, as thick, or more thick than thefirst metal layer when viewed in a cross sectional view of the die 4.

In various implementations, the semiconductor package 2 may include abackside metal layer 18 coupled to the second side 8 of the die 4. Thebackside metal layer 18 may be any metal disclosed herein, and invarious implementations, may include copper. In particularimplementations, the backside metal layer may include, by non-limitingexample, Ti/Ni/Cu, Ti/Cu, TiW/Cu, or any other type of metal stack ormetal alloy including copper. In various implementations, and asillustrated by FIG. 1, the length of the backside metal layer 18 may beless than the length of the die 4. In such implementations, the die 4may overhang the backside metal layer 18. In other implementations, thelength of the backmetal layer 18 may be substantially the same as thelength of the die 4 with the sides of the backmetal layer coextensivewith the sides/perimeter of the die. In still other implementations, theback metal layer may extend beyond the sides/perimeter of the die 4. Invarious implementations, the back metal layer may be patterned.

Still referring to FIG. 1, in various implementations the semiconductorpackage 2 may include a mold compound 20. The mold compound 20 may becoupled to the die 4. In various implementations, the mold compound mayinclude, by non-limiting example, an epoxy mold compound, an acrylicmold compound, or any other type of mold compound or protective coveringcapable of hardening and providing physical support and protection to asemiconductor device. In various implementations, the mold compound 20may cover a plurality of sidewalls 22 of the first metal layer 10 and aplurality of sidewalls 24 of the tin layer. In implementations with aplurality of bumps 16, the mold compound may cover a first side 26 and asecond side 28 of each bump. In various implementations, a surface 30 ofthe mold compound may be substantially coplanar and level with a surface32 of the tin layer 12. In various implementations, and as isillustrated by FIG. 1, the mold compound 20 may cover the sides of thedie. Specifically, the mold compound 20 may cover a third side 34 of thedie 4, a fourth side 36 of the die 4, a fifth side (oriented as goinginto the page in FIG. 1) of the die, and a sixth side (oriented ascoming off the page in FIG. 1) of the die. In the implementationillustrated by FIG. 1, the entirety of the sides of the die are coveredby the mold compound 20, however, in other implementations the sides ofthe die 4 may only partially be covered by a mold compound 20, while instill other implementations the mold compound 20 may not cover the sidesof the die 4. In various implementations, a portion of the second side 8of the die may be covered by a mold compound. The mold compound coveringthe second side of the die 4 may be the same or a separate mold compoundfrom the mold compound 20. In such implementations, the mold compound 20may also cover the sides of the backmetal layer 18 in implementationswhere the backmetal layer is the same length as or shorter than thelength of the die 4.

Referring to FIG. 2, a cross-section side view of a secondimplementation of a semiconductor package is illustrated. Thesemiconductor package of FIG. 2 may be similar to the semiconductorpackage of FIG. 1, with the difference being that the backside metallayer 40 may extend beyond the length of the die 42 and may becoextensive with the sides/perimeter of the semiconductor package 38.Further, as illustrated by FIG. 2, the backside metal layer 40 mayinclude multiple layers, and in particular implementations, may includethree layers. The backside metal layer may include, by non-limitingexample, a metal or metal alloy including titanium, nickel, silver,vanadium, copper, and any combination thereof. In particularimplementations, the backmetal layer 40 may include a layer includingtitanium, a layer including nickel, and a layer including a silvercopper alloy. In other particular implementations, the backmetal layermay include a layer including titanium, a layer including a nickelvanadium alloy, and a layer including a silver-copper alloy.

Referring to FIGS. 3A-3G, cross-section side views of a semiconductordevice following various steps of an implementation of a method forforming the semiconductor package of FIG. 1 are illustrated. Referringspecifically to FIGS. 3A-3B, a method for forming the semiconductorpackage of FIG. 1 may include forming a plurality of bumps/studs 44 on afirst side 46 of a wafer 48. More specifically, the method may includeforming a third metal 50 on the first side 46 of the wafer 48. The thirdmetal layer 50 may be any metal disclosed herein, and in particularimplementations, may include aluminum. The third metal layer 50 may bepatterned, as illustrated by FIG. 3A, however, in other implementationsthe third metal layer may not necessarily be patterned.

Referring to FIG. 3B, the method may include forming a first metal layer52 over the third metal layer 50. The first metal layer 52 may be anymetal disclosed herein, and in particular implementations, includescopper. The first metal layer 52 may be patterned, as illustrated byFIG. 3B, however, in other implementations the first metal layer may notbe patterned. In various implementations, the method may also includeforming a second metal layer 54 over the first metal layer 52. Thesecond metal layer 54 may be any metal disclosed herein, and inparticular implementations, includes tin. The second metal layer 54 mayalso include a solder material. The second metal layer 54 may bepatterned as illustrated by FIG. 3B, however, in other implementationswhere additional conductive layers cover the second metal layer 54, thesecond metal layer may not necessarily be patterned.

In various implementations, the method for forming the semiconductorpackage of FIG. 1 includes forming non-patterned metal layers over thefirst side 46 of the wafer 48. The method may then include etchingthrough any number of the metal layers, including all of the metallayers coupled over the first side 46 of the wafer 48, in order to formthe plurality of bumps 44. In various implementations, less than threemetal layers may be coupled over the first side 46 of the wafer 48, andin particular implementations, only a single metal layer may be formedand coupled directly to the first side 46 of the wafer 48. In otherimplementations, more than three metal layers may be formed over thefirst side 46 of the wafer 48. The metal layers coupled to the firstside 46 of the wafer 48 may be used to form any number of bumps over thewafer.

Referring specifically to FIG. 3B, the method for forming thesemiconductor package of FIG. 1 may include forming a plurality ofrecesses 56 into the first side 46 of the wafer 48 to a desired depthinto the wafer. In particular implementations, the depth of each recessof the plurality of recesses 56 may be less than 50 um, while in otherimplementations the depth may be 50 or more micrometers depending on thethickness of the wafer. In various implementations, the plurality ofrecesses 56 may be formed using a saw, a laser, a plasma etch, achemical etch, or any other method for forming a recess in a wafer. Inimplementations where an etch is used, the etch may be an etchingprocess marketed under the tradename BOSCH® (the “Bosch process”) byRobert Bosch GmbH, Stuttgart, Germany, may be used to form the pluralityof recesses 56 in the wafer 48. In such implementations, the sidewallsof the plurality of recesses 56 may be slightly patterned or ridgedwhich may facilitate adhesion of a mold compound to the sidewalls of theplurality of recesses 56. In various implementations, the plurality ofrecesses 56 may be positioned in the wafer 48 so that they are betweenthe semiconductor devices in the wafer.

Referring to FIG. 3C, the method for forming the semiconductor packageof FIG. 1 includes applying a mold compound 58 to the first side 46 ofthe wafer 48. The mold compound may include any type of mold compounddisclosed herein and may be applied using, by non-limiting example, aliquid dispensing technique, a transfer molding technique, a vacuummolding technique, a glob top molding technique, or a compressionmolding technique. In various implementations, and as illustrated byFIG. 3C, the mold compound 58 may encapsulate the plurality of bumps 44and fill the plurality of recesses 56. In other implementations, themold compound 58 may only be applied within the plurality of recesses 56and between the plurality of bumps 44 without flowing over the outersurfaces 60 of the plurality of bumps 44.

Referring to FIG. 3D, the method for forming the semiconductor packageof FIG. 1 may include thinning a second side 62 of the wafer 48 to thedesired depth of the plurality of recesses 56. In particularimplementations, the method may include backgrinding a second side 62 ofthe wafer 48 to reach the plurality of recesses 56 and singulate aplurality of die 64 from the wafer. In implementations where the secondside 62 of the wafer 48 is background, the backgrinding may use aprocess marketed under the trade name TAIKO by DISCO of Tokyo, Japan.The backgrinding leaves a ring of non-removed material (TAIKO ring)along the perimeter of the wafer which helps to prevent the wafer fromcurling, warping or otherwise bending during processing while at thesame time removing most of the thickness and material of the second side62, or backside of the wafer 48. The ring is then subsequently removedin a separate cutting step prior to singulation of the die. In otherimplementations of methods of forming semiconductor devices the TAIKOprocess may not be used, but some other backgrinding or othermaterial-removal technique may be used, such as removing the materialthrough a wet etch. In various implementations, the thinned wafer 48, orplurality of die 64, may be less than 50 um thick, while in otherimplementations the thinned wafer, or plurality of die, may be 50 ormore um thick. The mold compound 58 coupled to the first side 46 of thewafer 48 and within the plurality of recesses 56 may facilitate thinningthe wafer 48 by providing structural support to the wafer. In otherimplementations, the second side 62 of the wafer may not be thinned tothe depth of the desired recesses 56. In this manner, the die of eachsemiconductor package may be stepped upon singulating the wafer 48.

Referring to FIG. 3E, the method for forming the semiconductor packageof FIG. 1 may include coupling a backside metal layer 66 to the secondside 62 of the wafer 48 or to the second side of the plurality of die64. The backside metal layer 66 may be any type of metal disclosedherein, and in particular implementations, may include copper. Invarious implementations, the backside metal layer may be coupled to thesecond side of the wafer through an electroplating process. In otherimplementations, the backside metal layer may be coupled to the secondside of the wafer through a sputtering process or an electroplatingprocess. In still other implementations, the backside metal layer may bea metal frame/film coupled to the wafer through, by non-limitingexample, sintering, soldering, or fusion bonding. In variousimplementations, the backside metal layer 66 may be a thick backsidemetal layer and in particular implementations, may be as thick as orthicker than the thinned wafer 48. In various implementations, themethod for forming the semiconductor package of FIG. 1 may includeforming a plurality of openings 68 in the backside metal layer 66. Inother implementations, the backside metal layer 66 may not include anyopenings therein. In implementations where a plurality of openings 68are formed in the backside metal layer 66, the method may include,though not illustrated, applying a second mold compound to the secondside 62 of the wafer 48 that fills the plurality of openings 68. Thesecond mold compound may be the same as or different from the first moldcompound 58. In various implementations, the second mold compound mayalso encapsulate the backside metal layer 66. In such implementations,the method may include backgrinding the second mold compound to exposethe backside metal layer. In implementations with the second moldcompound applied to the second side 62 of the wafer 48, the entirety ofthe die of the singulated semiconductor may be at least partiallycovered by a mold compound on all six sides of the die. Inimplementations where the second side 62 of the wafer 48 is backgroundusing the Taiko process, the Taiko ring may be removed after thebackside metal is coupled to/formed on the second side of the waferusing a separate singulation process.

Referring to FIG. 3F, the method for forming the semiconductor packageof FIG. 1 may include exposing the outer surface 60 of the plurality ofbumps 44 through the mold compound 58 by grinding the mold compound 58.In various implementations, only the mold compound may be ground untilit is coextensive with the surface 60, however, in other implementationsthe mold compound and a portion of the plurality of bumps 44 may beground together. In this manner, the method may include planarizing theouter surface 60 of the plurality of bumps 44 with the outer surface 70of the mold compound 58. The backmetal layer 66 may facilitate thethinning of the mold compound 58 by adding structural support to thewafer 48 and the plurality of die 64. In various implementations, and asillustrated by the order of FIGS. 3C-3F, the second side 62 of the wafer48 may be thinned before the mold compound 58 is ground to expose theplurality of bumps 44, however, in other implementations the method mayinclude grinding the mold compound 58 to expose the plurality of bumpsbefore the second side 62 of the wafer 48 is thinned.

Referring to FIG. 3G, the method for forming the semiconductor packageof FIG. 1 includes singulating the mold compound 58 through theplurality of recesses 56 into a plurality of semiconductor packages 71.The mold compound may be singulated using a saw, a laser, a plasma etch,water jet cutting, a chemical etch, or any other method for cutting orremoving mold compound. In various implementations, the singulation line(or the width of the cut/etch made to singulate the mold compound) maybe less wide as compared to the width of each recess of the plurality ofrecesses 56. In such implementations, the sidewalls of each die of theplurality of semiconductor packages may be covered by the mold compound58. In implementations where the backside metal is not patterned, thebackside metal may be singulated along with the mold compound to formthe plurality of semiconductor packages.

Referring to FIGS. 4A-4C, cross-section side views of a semiconductordevice after steps of an implementation of a method for forming thesemiconductor package of FIG. 2 are illustrated. Referring specificallyto FIG. 4A, the method for forming the semiconductor package of FIG. 2may be similar to the method illustrated in FIGS. 3A-3G, with thedifference being that the method may include coupling a backside metallayer 72 to the second side 74 of the wafer 76 (or coupling a backsidemetal layer to a second side of the plurality of die), with the backsidemetal layer including multiple backside metal layers. In theimplementation illustrated by FIG. 4A the method includes coupling abackside metal layer 72 which includes three different backside metallayers. In various implementations, the backside metal layer 72 mayinclude more than or less than three backside metal layers. Each layerof the backside metal layer may be deposited to the wafer through, bynon-limiting example, a sputtering or evaporation technique. In variousimplementations, the backside metal layer may include, by non-limitingexample, titanium, nickel, silver, copper, vanadium, or any other metal.In particular implementations, the backside metal layer may include atitanium layer, a nickel layer, and a silver-copper layer. In otherparticular implementations, the backside metal layer may include atitanium layer, a nickel-vanadium layer, and a silver-copper layer. Invarious implementations, and as illustrated by FIG. 4A, the backsidemetal layer 72 may be patterned or may not be patterned.

Referring to FIG. 4B, the method for forming the semiconductor packageof FIG. 2 may include exposing the plurality of bumps 78 through themold compound 80 by grinding the mold compound. The plurality of bumpsmay be exposed using the same method or a similar method as describedabove in relation to FIG. 3F.

Referring to FIGS. 4A and 4C, the method for forming the semiconductorpackage of FIG. 2 includes singulating the mold compound 80 through theplurality of recesses 82 and the backside metal layer 72 into aplurality of semiconductor packages 84. The mold compound 80 and thebackside metal layer 72 may be singulated using any method disclosedherein. As the backside metal layer is not patterned, the sidewalls ofthe backside metal layer may be coextensive with the sides of therespective semiconductor packages 84.

The methods for forming semiconductor packages disclosed herein mayallow for the formation of thin die without needing a dual metallizationprocess for the purpose of stress balance. The mold compound and thebackside metal layer may offer the necessary support needed to handlethe thinned die and wafer during formation of the semiconductorpackages.

In places where the description above refers to particularimplementations of semiconductor packages and implementing components,sub-components, methods and sub-methods, it should be readily apparentthat a number of modifications may be made without departing from thespirit thereof and that these implementations, implementing components,sub-components, methods and sub-methods may be applied to othersemiconductor packages.

What is claimed is:
 1. A method for forming a semiconductor packagecomprising: forming a plurality of bumps on a first side of a wafer;forming a plurality of recesses into the first side of the wafer to adesired depth into the wafer; applying a mold compound to the first sideof the wafer, wherein the mold compound encapsulates the plurality ofbumps and fills the plurality of recesses; thinning a second side of thewafer to the desired depth of the plurality of recesses; coupling abackside metal layer to the second side of the wafer; exposing theplurality of bumps through the mold compound by grinding the moldcompound; forming a plurality of openings through the backside metallayer; and singulating the mold compound through the plurality ofrecesses into a plurality of semiconductor packages.
 2. The method ofclaim 1, wherein each bump of the plurality of bumps comprises a firstmetal layer and a second metal layer, wherein the first metal layer isbetween the second metal layer and the wafer.
 3. The method of claim 2,wherein the second metal layer comprises tin.
 4. The method of claim 2,wherein each bump of the plurality of bumps further comprises a thirdmetal layer, wherein the first metal layer comprises copper, the secondmetal layer comprises tin, and the third metal layer comprises aluminum.5. The method of claim 1, wherein the backside metal layer comprisescopper.
 6. The method of claim 1, further comprising planarizing theouter surface of the plurality of bumps with the outer surface of themold compound.
 7. The method of claim 1, wherein the second side of thewafer is thinned before the plurality of bumps are exposed.
 8. A methodfor forming a semiconductor package comprising: forming a plurality ofbumps on a first side of a wafer; forming a plurality of recesses intothe first side of the wafer; applying a mold compound to the first sideof the wafer, wherein the mold compound encapsulates the plurality ofbumps and fills the plurality of recesses; backgrinding a second side ofthe wafer to reach the plurality of recesses and singulate a pluralityof die from the wafer; coupling a backside metal layer to a second sideof the plurality of die; exposing the plurality of bumps through themold compound by grinding the mold compound; and singulating the moldcompound at the plurality of recesses to form a plurality ofsemiconductor packages.
 9. The method of claim 8, wherein each bump ofthe plurality of bumps comprises a first metal layer and a second metallayer, wherein the first metal layer is between the second metal layerand the wafer.
 10. The method of claim 9, wherein each bump of theplurality of bumps comprises a third metal layer.
 11. The method ofclaim 9, wherein the second metal layer comprises tin.
 12. The method ofclaim 8, wherein the backside metal layer comprises a metal includingone of titanium, nickel, silver, vanadium, copper, and any combinationthereof.
 13. The method of claim 8, further comprising planarizing theouter surface of the plurality of bumps with the outer surface of themold compound.
 14. The method of claim 8, wherein the second side of thewafer is background before the plurality of bumps are exposed.